of gelatine, it is found that this rigidity, enormous compared with that of water, is still, however, one trillion eight hundred and forty billion times less than that of steel.
This figure, exact within a few billions, proves that the rigidity is very slight, but exists; and that suffices for a characteristic distinction to be founded on this property.

In a general way, M.
Spring has also established that we meet in solids, in a degree more or less marked, with the properties of liquids.

When they are placed in suitable conditions of pressure and time, they flow through orifices, transmit pressure in all directions, diffuse and dissolve one into the other, and react chemically on each other.

They may be soldered together by compression; by the same means alloys may be produced; and further, which seems to clearly prove that matter in a solid state is not deprived of all molecular mobility, it is possible to realise suitable limited reactions and equilibria between solid salts, and these equilibria obey the fundamental laws of thermodynamics.
Thus the definition of a solid cannot be drawn from its mechanical properties.

It cannot be said, after what we have just seen, that solid bodies retain their form, nor that they have a limited elasticity, for M.Spring has made known a case where the elasticity of solids is without any limit.
It was thought that in the case of a different phenomenon--that of crystallization--we might arrive at a clear distinction, because here we should he dealing with a specific quality; and that crystallized bodies would be the true solids, amorphous bodies being at that time regarded as liquids viscous in the extreme.
But the studies of a German physicist, Professor O.Lehmann, seem to prove that even this means is not infallible.